Multireference generalized Van Vleck perturbation theory (GVVPT2) study of the NCO + HCNO reaction: insight into intermediates.

Possible mechanisms for the NCO + HCNO reaction, previously studied using single reference methods, have been revisited using the second-order generalized Van Vleck perturbation theory (GVVPT2) variant of multireference perturbation theory. Large scale GVVPT2 calculations, with 25 active orbitals, demonstrate that the electronic structures of the ground states of all eight previously identified plausible doublet spin intermediates of this reaction are substantially multiconfigurational with maximum configuration amplitudes not larger than 0.87.